I don't know if this is a bug or a limitation, but MCOMMAND_PHONGTOSELECTION selects edges only if their phong is broken manually using MCOMMAND_BREAKPHONG command. I need to select all phong break edges based on actuall phong tag, or by manually defining the angle.

Hi @merkvilson, this is a limitation actually the tool Phong Break selection and the modeling command MCOMMAND_PHONGTOSELECTION are two completely separate things.
So the only solution available to you is to manually break the Phong.

I'm sorry we can't help you more on that, Donovan points you to the correct direction with the neighbor class.
Cheers,
Maxime.